let runningTotal = 0;
let buffer = "0";
let previousOperator;
const screen = document.querySelector('.screen');
function buttonClick(value){
if(isNaN(value)){
handleSymbol(value);
}else{
handleNumber(value);
}
screen.innerText = buffer;
}
function handleSymbol(Symbol){
switch(Symbol){
case 'C':
buffer = '0';
runningTotal = 0;
break;
case '=' :
if(previousOperator === null){
return
}
flushOperator(parseInt(buffer));
previousOperator = null;
buffer = runningTotal;
runningTotal = 0;
break;
case '←':
if(buffer.length === 1){
buffer = '0';
}else{
buffer = buffer.substring(0,buffer.length - 1);
}
break;
case '+':
case '-':
case '×':
case '÷':
handleMath(Symbol);
break;
}
}
function handleMath(symbol){
if(buffer ==='0'){
return;
}
const intBuffer = parseInt(buffer);
if(runningTotal ===0){
runningTotal = intBuffer;
}else{
flushOperator(intBuffer);
}
previousOperator = symbol;
buffer = '0';
}
function flushOperator(intBuffer){
if(previousOperator === '+'){
runningTotal += intBuffer;
}else if(previousOperator === '-'){
runningTotal -= intBuffer;
}else if(previousOperator === '×'){
runningTotal *= intBuffer
}else if(previousOperator === '÷'){
runningTotal /= intBuffer;
}
}
function handleNumber(numberString){
if(buffer === '0'){
buffer = numberString;
}else{
buffer += numberString;
}
}
function init(){
document.querySelector('.calc-buttons').addEventListener('click',function(event){
buttonClick(event.target.innerText);
})
}
init();